linux-kernel - Re: [PATCH -next] mm/filemap: fix that first page is not mark accessed in filemap

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Date:   Thu, 9 Jun 2022 08:59:47 +0800
From:   Yu Kuai <yukuai3@...wei.com>
To:     <willy@...radead.org>, <akpm@...ux-foundation.org>,
        <kent.overstreet@...il.com>
CC:     <axboe@...nel.dk>, <linux-fsdevel@...r.kernel.org>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <yi.zhang@...wei.com>
Subject: Re: [PATCH -next] mm/filemap: fix that first page is not mark
 accessed in filemap_read()

friendly ping ...

在 2022/06/02 16:21, Yu Kuai 写道:
> In filemap_read(), 'ra->prev_pos' is set to 'iocb->ki_pos + copied',
> while it should be 'iocb->ki_ops'. For consequence,
> folio_mark_accessed() will not be called for 'fbatch.folios[0]' since
> 'iocb->ki_pos' is always equal to 'ra->prev_pos'.
> 
> Fixes: 06c0444290ce ("mm/filemap.c: generic_file_buffered_read() now uses find_get_pages_contig")
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> ---
>   mm/filemap.c | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 9daeaab36081..0b776e504d35 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2728,10 +2728,11 @@ ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter,
>   				flush_dcache_folio(folio);
>   
>   			copied = copy_folio_to_iter(folio, offset, bytes, iter);
> -
> -			already_read += copied;
> -			iocb->ki_pos += copied;
> -			ra->prev_pos = iocb->ki_pos;
> +			if (copied) {
> +				ra->prev_pos = iocb->ki_pos;
> +				already_read += copied;
> +				iocb->ki_pos += copied;
> +			}
>   
>   			if (copied < bytes) {
>   				error = -EFAULT;
>